Graphite article

ABSTRACT

A graphite article which can be compressed by more three (3%) percent at a contact pressure of 100 KPa or less without damaging the graphite article reducing the thermal impedance exhibited by the article. Also a graphite article comprising graphitized polymer having a thickness of at least 75 microns. Preferably the graphite has a density of less than 1.50 g/cc and a compressibility of more than 3% at a contact pressure of 100 KPa. Also the article has a generally sheet like shape. These articles may be used in a thermal management system to dissipate heat from a heat source.

This application claims priority to U.S. Provisional App. No.61/899,998, filed on Nov. 5, 2013. The benefit of priority to theaforementioned application is hereby claimed under at least 35 U.S.C. §365.

The article described herein relates generally to the field of graphitearticles, in particular graphite articles which may have applications inthermal management systems.

TECHNICAL BACKGROUND

Graphite articles have been used in the thermal management for variousdevices. Such prior uses of graphite have included the dissipation ofheat in the z direction away from the heat source or the spreading ofheat in x-y direction away from a hot spot exhibited on the heat source.

In the case of dissipating heat in the z direction, conventional wisdomis to minimize the distance between the heat source and the heatdissipation element. This is accomplished by minimizing the thickness ofthe graphite article and in accordance with conventional wisdom therebyminimizing the thru-body thermal impedance of the article.

BRIEF DESCRIPTION

An embodiment included herein is a graphite article which can becompressed by more three (3%) percent at a contact pressure of 100 KPaor less without damaging the graphite article reducing the thermalimpedance exhibited by the article.

Another embodiment includes a graphite article comprising graphitizedpolymer having a thickness of at least 50 microns. Preferably thegraphite has a density of less than 1.50 g/cc and a compressibility ofmore than 3% at a contact pressure of 100 KPa. Also the article has agenerally sheet like shape.

It is to be understood that both the foregoing brief description and thefollowing detailed description provide embodiments of the disclosure andare intended to provide an overview or framework of understanding tonature and character of the invention as it is claimed.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an article described herein.

FIG. 2 is a cross sectional view along line A-A of FIG. 1 rotated alongarrow B.

FIG. 3 is a cross sectional view along line A-A of FIG. 1 rotated alongarrow B of an alternate embodiment of FIG. 2.

FIG. 4 is a side view of another article described herein.

FIGS. 5-5(c) are schematic views of various embodiments of a thermalmanagement system which include the graphite article disclosed herein.

FIG. 6 is a schematic view of another embodiment of a thermal managementsystem which includes the graphite article.

DETAILED DESCRIPTION

An article disclosed herein includes a graphite article having agenerally sheet like shape. The article comprises a graphitized polymerhaving a thickness of at least 50 microns preferably at least 75microns. The thickness of the article may range upwards to 300 microns.Optional exemplary thickness can include at least 75 microns, at least100 microns, at least 150 microns, at least 200 microns, at least 250microns or any other desired thickness. The density of the graphite istypically less than 1.50 g/cc. For any given embodiment of the articlethe density may range from less than 1.25 g/cc to about 0.3 g/cc, asdesired for the end application. It should be understood that alldensities between such range end points are disclosed herein and arepossible. Exemplary densities include less than 0.4 g/cc, less than 0.5g/cc, less than 0.6 g/cc, less than 0.7 g/cc, less than 0.85 g/cc, lessthan 1.0 g/cc and less than 1.25 g/cc.

The article has a compressibility of more than 3% at a contact pressureof 100 KPa. Exemplary compressibility for a given embodiment may rangefrom more than 3% to up to 75%. Particular examples of compressibilityinclude more than 5%, more than 10%, more than 20%, more than 25%, morethan 30%, and up to 65%. To provide a non-limiting example of meaning ofthe compressibility numbers, if the compressed thickness is 35% of theoriginal thickness, the article has exhibited a compressibility of 65%.

The testing of the compressibility of the article is not limited to anyparticular method or apparatus. Exemplary apparatuses that may be usedto test compressibility include a Greening Model 1140 CompressibilityTest Machine and Test Machine Inc. (“TMI”) Compression Tester Models17-76 or 17-77. This reduction in thickness may be a permanent reductionin thickness without rupture or other destruction of the article. In thecase compressibility is measured by measuring a change in thickness ofthe article, a Mahr Extreme Thickness Test Instrument may be used.

Optionally, the article may include one or more dopants. One such dopantmay be a conductive polymer, another dopant may include an EMI modifier.Examples of EMI dopants include nickel, copper, mu-metals andcombinations thereof. Mu-metals are nickel-iron alloys which have highmagnetic permeability. The conductive polymer may also have thebeneficial property of wetting out on the surface of the article.Non-limiting examples of the polymer may include oil or a polymer filledwith a conductive material. Other dopants include a phase changematerial or a dielectric material. In the case of the article includingan oil, a grease or a phase change material (non-limiting example a wax)it is preferred that the article includes a sufficient amount of oil,grease or phase change material to reduce the contact resistance thearticle would exhibit in an application as a thermal interface betweenone or more heat sources and a heat dissipating element. The dopants maybe in the form of a liquid, particles, powder or filaments. Anon-limiting exemplary embodiment is that the article includes at least5% by weight of the dopant. When the article includes a dopant, one ormore surfaces of the graphite which make up the article may includeperforations, notches, cutouts and combinations thereof. This may bereferred to as alternations. Preferably the alterations are sized,shaped and located to assist with mechanical inclusion of the dopant inthe graphite. Examples of functions of the alternations include thatthey may be used to impregnate the entire article with the dopant or twolocate the dopant on one or more surfaces of the article. Article 10 isshown in FIG. 4 having a plurality of cut outs 22 on a major surface 24of article 10. As shown the cutouts have a substantially dove tailconfiguration. The cutouts contemplated herein are not limited to anyparticular orientation.

Once again when used in a thermal interface application, the article mayexhibit a resistivity of less than 0.019° C./W at a contact pressure ofat least 200 KPa. Examples of suitable resistivity include less than0.015° C./W, less than 0.010° C./W, and less than 0.08° C./W, asmeasured on an apparatus that meets the requirements of ASTM D5470Standard Test Method.

At a contact pressure of at least 700 KPa, the graphite article exhibitsa total thermal impedance of no more than 0.25 cm²° C./W, preferably nomore than 0.20 cm²° C./W. Total thermal impedance is a measure of thecontact impedance and the thru-body impedance an article exhibits.

In another embodiment, as the contact pressure increase from 100 KPa to700 KPa, the total thermal impedance exhibited by the graphite articlereduces by a factor of at least 6, preferably at least 7, even morepreferred at least 8.

Another advantage of the afore noted graphite article is that as thecontact pressure exerted on the article may increase the in-planethermal conductivity of the article. For example as the contact pressureincreases from 100 KPa to 700 KPa, the in-plane thermal conductivityexhibited by the article may increase at least 1.25 times, preferably atleast 1.5 times, more preferably up to at least 2 times.

The article may be a monolithic article; monolithic is used herein tomean that the article does not include multiple sheets of graphite toachieve the desired thickness. Alternatively stated, the article mayconsist essentially of a single sheet of graphite. A further way tostate this is that the article may be devoid of more than one sheet ofgraphite.

In a different embodiment, the article may comprise more than one of theaforementioned graphite sheets. Preferably each graphite sheet isoriented such that the x-y plane of the each individual graphite sheetis in the horizontal direction of the article and not in the verticaldirection of the article. The various sheets may be stacked to anydesired thickness. In such an embodiment, optionally, a thermoplasticsheet may be disposed between adjacent graphite sheets. In the case ofan article that includes “N” number of graphite sheets, the article mayinclude up to “N−1” thermoplastic sheets, wherein each thermoplasticsheet is disposed between two (2) different graphite sheets.

The article is not limited to only including graphite. The article mayinclude an adhesive on one or more of the surfaces of the article. Forexample, the article may include an adhesive on one or more of the majorsurface of the article. The adhesive may be applied completely on one ofthe major surface of the article. Alternatively the adhesive may beapplied in a picture frame orientation, such as to a sufficient exteriorportion of the perimeter of the major surface as shown in FIGS. 1 and 2.As illustrated in FIG. 1, article 10 includes a graphite sheet 12, witha major surface 14. Adhesive 16 is applied to a perimeter section ofmajor surface 14. FIG. 2 is a cross-sectional view along line A-A ofFIG. 1 and rotated in the direction of arrow B. In another embodiment,the adhesive may be applied to three (3) or less of the edge sections ofthe perimeter of the major surface, as shown in FIG. 3. If so desiredthe article 10 may be sized such that the heat source may engageadhesive 16 or that the heat source will fit inside of the adhesive todirectly engage the exterior graphite portion of article 10.

The article may alternatively or in combination with the adhesiveinclude a first thermoplastic layer on one of the major surfaces of thearticle. A second thermoplastic layer may be on the other major surfaceof the article. If so desired the first, second, or both thermoplasticlayers may form an exterior surface of the article. In a particularembodiment of the article, the thermoplastic layer will not be locatedon a major surface disposed in thermal contact with a heat source.Stated another way, the thermoplastic layer may be disposed on the majorsurface planned to be opposed to the heat source.

In a further particular embodiment, if so desired, the article may beenvelope sealed with the thermoplastic. Envelope sealed can be used todescribe when the thermoplastic layers extend beyond the edges of thegraphite sheet, such that the graphite sheet of the article ishermetically enclosed in the thermoplastic sheets. In a particularenvelope sealed embodiment, the thermoplastic sheet or sheets may form aframe around the a desired portion of the perimeter of the article,thereby leaving an central portion of the graphite article on each majorsurface not covered by a thermoplastic layer. Optionally, only one majorsurface of the graphite article may be covered with the aforementionedframe envelope seal.

In a particular embodiment, the article has a bond line thickness ofless than 0.127 mm. The bond line thickness is the entire thickness ofthe article.

The article may be included in a thermal management system. One majorsurface of the article has a substantially similar contact surface areaas a contact surface area of a heat source to which that the article isin thermal contact with. A non-limiting list of examples of heat sourcesinclude electronic components such as CPUs, GPUs, a driver chip, amemory chip, RF power amplifiers, transceivers, DC/DC switchers, PMIC(Power Management IC), Buck and/or Boost inductors, power converters,wireless charging elements, image processing and stabilizing elements,still or video image lighting sources, LEDs, disk drives, andCD/DVD/Blue-Ray drives. Preferably, the second major surface of thearticle may be in thermal contact with a heat dissipation element.Non-limiting examples of a heat dissipation element include a heat sink,a heat spreader, a heat pipe, a cold plate, a frame for an electronicdevice, a chassis for an electronic device. The article is equallyapplicable to lighting applications, telecommunications applications aswell as OLED devices. In a further alternate embodiment, the contactsurface of the article may be larger than the contact surface area ofthe device in which it is in contact.

The above article may be incorporated into an electronic device invarious ways. A few examples of how the article may be used in such adevice will be discussed below.

Shown in FIG. 6 is a thermal management system 40 for an electronicdevice. Thermal management system 40 dissipates heat from heat source42, the heat source may be any one of the above examples of a heatsource. In system 40, a graphite article 44 is in thermal contact withheat source 42. The system may further include one or more furthergraphite articles 44. As shown, each graphite article 44 is in thermalcommunication with another graphite article 44. As shown the adjacentgraphite articles do not have major surfaces with the same area. Asshown the middle graphite article 44′ is disposed in alignment with thetop surface of an RF can 46. Graphite article 44′ may be sized to fitthrough an opening in can 46. As shown each major surface of graphitearticle 44′ is not sized to have substantially the same surface area asthat of the graphite articles 44 and 44″ which it is in thermalcommunication. Lastly, the graphite articles 44 most opposed to heatsource 42 can be in thermal communication with a heat dissipationelement 48. As shown the graphite article 44″ optionally does not needto have a major surface with the same surface area as the heatdissipation element it is in thermal contact with. The heat dissipationelement may have a surface having a larger surface area than the surfacearea of the major surface of graphite article 44″ in thermal contactwith element 48.

Another version of a thermal management system 50 is shown in FIG. 5.Thermal management system 50 may include a heat dissipation element 52.Dissipation element 52 may be in contact with a graphite article 44. Insystem 50, instead of having element 44′, system 50 includes a layer ofmaterial having one of smaller versions of article 44, noted as element44 a and one of more gap pads 54. As shown the layer may include two (2)graphite articles 44 a and three (3) gap pads 54. The layer ofembodiment 50 may include any desired combination and orientation of gappads 54 and graphite articles 44 a.

System 50 may also include a contact element 56 in thermal communicationwith the layer. The contact element may include any one of the followingor a combination thereof, an isotropic material, a laminate of aisotropic material and the graphite article, a laminate of the graphitearticle—the isotropic material—the graphite article, or a laminate ofthe graphite article—an isotropic material—the graphite article having adopant on or in the graphite article in closest to the heat source.Examples of the isotropic material may include any type of metal ormetal alloy, such as but not limited to steel, aluminum, copper, alloysthereof and combinations thereof. Contact element 56 is in thermalcontact with a heat source.

In FIG. 5(a), system 50 is in thermal contact with the top of an RF canlid 57. In FIG. 5(b) system 50 is thermal contact with a top surface ofa heat source 58. Also shown in FIG. 5(b) is a pair of RF can sidewalls59 are adjacent heat source 58. The thermal system 50 may or may not bein contact with the pair of RF can sidewalls. Having thermal system 50in contact with the RF can sidewalls 59 is shown in FIG. 5(c).

If so desired, the article may include a phase change material such as awax or any other known phase change materials. Other materials which maybe included in the article include a grease, an oil or a polymer. If sodesired such materials may be used in combination. The material may becoated onto the article and/or impregnated into the article.

Also disclosed herein is a method of making an electronic device. Themethod may include disposing the article in operative thermal contact toone of a heat source or a heat dissipation element. Next the article isdisposed in operative thermal contact to the other of the heat source orthe heat dissipation element not attached to in the prior step. Theattaching results in the article being compressed by at least 3% with acontact pressure of at least 50 KPa. The compression of the article maybe by at least 10%. The article itself may be by at least 20 microns.Examples of the amount of compression of the article may be at least 50microns, at least 75 microns, at least 100 microns. The amount ofcompression may be determined by the change in thickness of the article.Operative thermal contact is used herein to mean that the articlereceives heat from the heat source in the first step above and in thesecond step it transmits heat which eventually is transmitted to theheat dissipation element. Stated another way, the article facilitatesthe heat path from the heat source to the heat dissipation element. Thearticle may be in actual physical contact with either or both of theheat source, but such physical contact is not required to practice theabove method.

Also disclosed herein is an article that may be used as a thermalinterface. The article will have a density of less than 1.50 g/cc, athickness of at least 75 microns, a through plane conductivity ofgreater than 2 W/mK and a compressibility of at least 3%, preferably acompressibility of at least 5%. The thermal conductivity preferably maybe at least 3 W/mK, more preferably at least 5 W/mK. The abovedescription of properties regarding density, thickness andcompressibility are equally applicable to this embodiment and areincorporated herein by reference as if fully written. ASTM D5470 may beused to determine the aforementioned thermal conductivity at a contactpressure of at least 50 KPa. In a further embodiment, the aforementioneddensity may be no more than 1.25 g/cc.

Various methods which can be used for making a graphite article havinggraphitized polymer are disclosed below.

A process for making a graphite film may comprises the following threesteps: (1) providing a polymer film wherein the polymer selected shouldbe graphitizable; (2) thermally treating the polymer film at a definedrange of temperature under pressure conditions to obtain a graphitefilm; and (3) subjecting the graphite film to rolling.

In the first step, there is provided a polymer film selected frompolyamide (PA), polyphenyleneoxadiazoles, polyoxadiazole (POD),polybenzothiazole (PBT), polybenzobisthiazole (PBBT), polybenzoxazole(PBO), polybenzobisoxazole (PBBO), polyimide (a non-limiting examplebeing a poly(pyromellitimide)) (PI), poly(phenyleneisophthalamide)(PPA), polybenzimidazole, polybenzobisimidazole,poly(phenylenebenzoimidazole) (PBI), poly(phenylenebenzobisimidazole)(PPBI), polythiazole (PT), and poly(para-phenylenevinylene) (PPV) andcombinations thereof. The polyphenyleneoxadiazoles includepoly-phenylene-1,3,4-oxadiazole and isomers thereof.

In one embodiment, the starting film may have a thickness of up to 400μm. A range of typical examples of the thickness of the starting filmmay be from 25 to 200 μm.

The starting polymer film is thermally treated at a final treatingtemperature of not lower than 2400° C. The starting film may bepre-heated for carbonization prior to the final thermal treatment. Forinstance, the film may be pre-heated at a heating rate of 2° to 50°C./min up to 1000° C. and kept at the temperature for a time sufficientfor the carbonization. The pre-heating is preferably done in an inertgas such as nitrogen, argon or the like. The time for the thermaltreatment at 2400° C. or higher can vary depending on the actualtemperature used and the type of starting film.

For thermal treatment in a temperature range over 1600° C., this mayoccur in an inert gas of the type as mentioned above at normal pressuresor under pressure. Examples of The pressures that may be used for thetreatment are generally in the range of from 0.1 kg/cm² to 50 kg/cm².The pressure may be applied isotropicly, in a manner that allows theformation of a graphite film which is foamed owing to the generation ofgas but the foaming is generally uniform as a whole.

The graphitized film may be subjected to rolling. The rolling procedureis usually carried out by calendaring the film. The rolling may beconducted at normal temperatures or elevated temperatures and optionallyat a linear or nip pressure of not less than 2 kg/cm.

Another method for making the graphite film includes the step of holdingthe polymeric film in a vessel being directly electrifiable by voltageapplication; and graphitizing the polymeric film in the vessel byapplying a voltage to the vessel so as to carry out electrification.This results in voltage application to and electrification of thepolymeric film thereby causing heat generation of the polymeric film. Asa result, an electric resistance is lowered as the polymeric film iscarbonated. As the electric resistance is lowered, current flows throughthe polymeric film. Due to the resultant Joule heat, heat is generatedin the raw material. As a result, an inside and a surface portion of thefilm are uniformly heated. The electrifiable vessel also heats the filmfrom the film's surrounding sufficiently and uniformly.

The carbonized polymeric film can be obtained by preheating a polymericfilm, which is a starting material, under reduced pressure or an inertgas. The preheating may be carried out at a temperature of approximately1000° C. For example, it is preferable that the polymeric film is heatedat a temperature of approximately 1000° C. for 30 minutes with a ramprate of 10° C./minute.

The vessel may further include carbon powder inside the vessel. Thecarbon powder may be used to fill the void space between the vessel andthe polymeric film. This may further enhance conductivity of theelectricity to the polymeric film. Thus the carbon powder may functionas a conductor, conducting electrical energy into the polymeric film.

In addition to the above or alternatively, the polymeric film may besandwiched by metal plates or graphite plates, and the sandwichedpolymeric film thus sandwiched and brought into contact with a wall orthe bottom of the vessel, and optionally any carbon powder included inthe vessel. Except for weight of the metal plates or graphite plates, noparticular additional pressure need be exerted on the polymeric film. Inone particular embodiment which includes carbon powder, the powder maybe fully around the interior of the vessel. Stated another way, thepolymeric films are held respectively in directly electrifiable vesselsand the carbon powder is provided on and around the inner portion of thedirectly electrifiable vessels so as to fill gaps between the polymericfilm and the electrifiable vessel.

The voltage that may be applied may be either AC or DC voltage. Anexample of a current that may be used is a current of 10 mA or greaterflows into the polymeric film as a result of the electrification. Theaforementioned current is just an exemplary embodiment and othercurrents are equally applicable.

A further process for producing a graphite film includes thermaltreating a polymer film at a temperature of 2,000° C. or more, theprocess comprising the step of bringing a polymer film into contact witha substance containing a metal during thermal treatment. An alternativeprocess for producing a graphite film in which a polymer film isthermally treated at a temperature of 2,000° C. or more, includes thestep of bringing a carbonized polymer film into contact with a substancecontaining a metal during thermal treatment. Further for producing agraphite film in which a polymer film is brought into contact with acontainer and thermally treated at a temperature of 2,000° C. or more,wherein the container contains a metal. The container can be a closedcontainer.

The phrase “the container can be closed” means that the film can besurrounded on four or six sides by the container so that the polymerfilm and/or the carbonized polymer film can be sufficiently brought intocontact with a substance containing a metal. Atmospheric gas around thepolymer film and/or the carbonized polymer film may be expanded as thetemperature is increased. It is preferable to ensure a place where theatmospheric gas can escape. Accordingly, the phrase “the container canbe closed” in the present invention does not mean that the container isin a completely closed state in which the container is broken by thepressure of expanded atmospheric gas.

The aforementioned metal may be one or more selected from the groupconsisting of elements of Groups 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13such as aluminum and boron according to the IUPAC (International Unionof Pure and Applied Chemistry) Nomenclature of Inorganic Chemistry,revised edition (1989), lithium, beryllium, sodium, magnesium,potassium, calcium, barium, silicon, germanium, selenium, tin, lead andbismuth and combinations thereof. Further the metal may be one or moreselected from the group consisting of titanium, vanadium, chromium,manganese, iron, cobalt, nickel, copper, zinc, zirconium, niobium,molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium,hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold,mercury and combinations thereof.

The thermal treatment may have a step of carbonizing a polymer film anda step of graphitizing the polymer film. Carbonization andgraphitization may be performed either separately or continuously.

Carbonization is performed by pre-heating a polymer film as a startingmaterial under reduced pressure or in nitrogen gas. The pre-heating iscarried out typically at a temperature of 800 to 1,500° C. The highesttemperature of carbonization may be maintained for about 30 minutes toone hour after reaching the highest temperature. For example, when thefilm is heated at a rate of 10° C./min, the temperature of the film maybe maintained in a temperature range of 1,000° C. for about 30 minutes.Optionally pressure may be applied in the direction perpendicular to thefilm surface.

Graphitization may be carried out by once removing a carbonized polymerfilm and transferring the film in a graphitization furnace, or may becarried out continuously from carbonization. Graphitization is carriedout under reduced pressure or in an inert gas. Argon or helium isappropriate for the inert gas. The thermal treatment temperature may beat least 2,000° C. or more. The final thermal treatment temperature ispreferably 2,400° C. or more, more preferably 2,600° C. or more, andstill more preferably 2,800° C. or more.

The thermal treatment may be carried out by fixing the polymer film to acontainer. The container may be made of graphite. Graphite hereinincludes, in a broad sense, a material containing graphite as a maincomponent insofar as the material can be heated to the above temperaturerange. Graphite may be isotropic graphite or extruded graphite, forexample. When graphite is repeatedly used, isotropic graphite havingexcellent electrical conductivity, thermal conductivity and uniformityis preferable. The container may have any shape such as a shape of asimple flat plate. The container may also have a shape of a cylinder,and the polymer film may be wound around the container. The shape of thecontainer is not specifically limited insofar as the polymer film can bebrought into contact with the container.

The method of bringing the polymer film into contact with the inside ofa container made of graphite (including a method of holding or fixingthe film) may be each of a method of sandwiching the polymer film in agraphite or metal plate and bringing the film into contact with the wallor bottom of the container while pressure other than the own weight ofthe plate is not applied to the polymer film (in which the polymer filmmay be held by or fixed to the container) and a method of winding thepolymer film around a cylindrical graphite container. However, themethod of making the article is not necessarily limited to thesemethods.

A polymer film may be graphitized by two steps of carbonization andgraphitization. First, carbonization generally refers to a process inwhich a polymer film is thermally treated to 1,000° C. to convert thefilm into a substance containing carbon as a main component.Specifically, when the polymer film is thermally treated at adecomposition temperature, the bond is cleaved and the decomposedcomponent leaves as a gas such as carbon dioxide, carbon monoxide,nitrogen or hydrogen. When the film is thermally treated to 1,000° C.,the film is a material containing carbon as a main component. Second,graphitization refers to a process in which a carbonaceous material isthermally treated at a temperature of 2,800° C. or more to convert thematerial into a structure having many graphite layers stacked, eachlayer of which has aromatic rings flatly connected with each other.

The material described herein may have any to all of the followingadvantages: low contact resistance, excellent thru-thickness thermalconductivity, high in-plane thermal conductivity and relatively highbond line thickness. One advantageous is as a large area thermalinterface material. Other advantageous of the material include lowerthermal resistance, increased compressibility and higher in-planethermal conductivity than conventional thermal interface materials.

Applications for the article may include being used as a thermalinterface in such environments as consumer electronics, white goods,drivetrains for automotive, commercial or locomotive vehicles,telecommunications, thermo-electronic devices, and industrial equipment.

The above description is intended to enable the person skilled in theart to practice the invention. It is not intended to detail all thepossible variations and modifications that will become apparent to theskilled worker upon reading the description. It is intended, however,that all such modifications and variations be included within the scopeof the invention that is defined by the following claims.

Thus, although there have been described particular embodiments of thepresent invention of a new and useful applications of a graphite articleand how to make such graphite article, it is not intended that suchreferences be construed as limitations upon the scope of this disclosureexcept as set forth in the following claims. The various embodimentsdiscussed above may be practiced in any combination thereof.

1-15. (canceled)
 16. A compressible graphite article comprising agraphitized polymer sheet having a thickness of at least 200 microns, adensity of less than 1.00 g/cc, and a thermal impedance of no more than0.25 cm²° C./W at a contact pressure of at least 700 kPa.
 17. Thegraphite article of claim 16 wherein the thickness comprises up to 500microns.
 18. The graphite article of claim 16 having a resistivity ofless than 0.019 (° C./W) at a contact pressure of at least 200 KPa. 19.The graphite article of claim 16, wherein as the contact pressure of thegraphite article increases, the in-plane thermal conductivity increases.20. The graphite article of claim 16, wherein as the contact pressure ofthe graphite article increases from 100 KPa to 700 KPa, the in-planethermal conductivity increases by at least 1.25 times.
 21. The graphitearticle of claim 16 further comprising a graphitized polymer having nodopant.
 22. The graphite article of claim 16 wherein the thicknesscomprises up to 300 microns.
 23. An electronic device comprising thegraphite article of claim
 16. 24. The electronic device of claim 23,whereby the graphite article in operative thermal contact with at leastone of a heat source and a heat dissipation element.
 25. The electronicdevice of claim 24, whereby the graphite article in compressed operativethermal contact with the at least one of a heat source and a heatdissipation element.
 26. A method of making a thermal management systemcomprising disposing the graphite article of claim 16 in operativethermal contact with a heat source.
 27. The method of claim 26 furthercomprising disposing the graphite article in operative thermalcommunication with a heat dissipation element.
 28. A method of making athermal management system comprising compressing a compressible graphitearticle comprising a graphitized polymer sheet having a thickness of atleast 200 microns, a density of less than 1.00 g/cc, and a thermalimpedance of no more than 0.25 cm²° C./W at a contact pressure of atleast 700 kPa in operative thermal communication with a heat source. 29.The method of claim 28 further comprising disposing the graphite articlein operative thermal communication with a heat dissipation element. 30.A method of making an electronic device comprising attaching a graphitearticle having a thickness of at least 200 microns, a density of lessthan 1.00 g/cc, and a thermal impedance of no more than 0.25 cm²° C./Wat a contact pressure of at least 700 kPa to an electronic component,whereby the graphite article in thermal communication with theelectronic component.
 31. The method of claim 30 wherein the electroniccomponent comprises at least one of a heat source or a heat dissipationelement.